1. Field of the Invention
The present invention relates to a configuration of a mobile phone terminal, and to a peripheral unit for acoustic test of the mobile phone terminal, which connects the mobile phone terminal with a terminal acoustic evaluation unit for conducting an evaluation test of the acoustic characteristics of the mobile phone terminal.
2. Description of Related Art
To maintain speech quality of a mobile phone terminal, characteristic evaluations of various digital speech signal processors are carried out. These evaluations include frequency characteristic evaluations of its microphone and receiver (speaker), characteristic evaluations of an analog acoustic system such as an amount of acoustic echo occurring between the receiver and microphone, coding and decoding characteristic evaluations of a speech coder/decoder used by the mobile phone terminal, and echo elimination performance evaluations of an acoustic echo canceler. A peripheral unit for acoustic test is used for connecting the mobile phone terminal with a terminal acoustic evaluation unit for carrying out these characteristic evaluations.
As a conventional technique, there is a method of connecting a GSM (Global System for Mobile Communication) mobile phone terminal with a system simulator as described in GSM 04.14 of ETSI (European Telecommunication Standards Institutes) standards. The system simulator has the following functions as a party station of the mobile phone terminal to be evaluated. First, it can establish between it and the mobile phone terminal a TDMA radio connection identical to that used in an actual channel, and transmits and receives a speech code sequence using the channel. Besides, it transmits and receives a separate terminal control signal and a PCM digital speech signal using a dedicated port called DAI (Digital Audio Interface: abbreviated to DAI ports from now on). The mobile phone terminal and system simulator each comprise a DAI port composed of a dedicated 25-pin DSUB socket in accordance with ISO 2110 standard, and the two DAI ports are connected by a cable with connectors matching the shape of the ports.
The GSM 04.14 of the ETSI standards also specifies individual conditions such as electrical signal conditions, signal timings, and logical interfaces. Its signal transmission rate is specified at 104 kbits/second in both directions from the mobile phone terminal to the system simulator and from the system simulator to the mobile phone terminal. It is based on the calculation of 8000 (samples/second)×13 (bits/sample)=104,000 (bits/second) assigned to an evaluation speech signal. Using the specified shape of connectors and the unique transmission rate, the DAI ports are not connectable directly to a cable with connectors corresponding to various types of general purpose ports (such as USB, IEEE1394, RS-232C and RS423) which are widely used as external connecting ports of various types of current computer systems.
As for the GSM mobile phone terminal, three types of acoustic evaluation tests can be achieved by interconnecting the mobile phone terminal with the system simulator using the DAI ports, and by establishing a radio connection at the same time. The three types of acoustic evaluation tests will now be described with reference to FIGS. 10-14.
FIG. 10 is a block diagram showing a device connection state at a terminal acoustic evaluation test in a conventional GSM mobile phone terminal. In FIG. 10, the reference numeral 1 designates a mobile phone terminal, 2 designates a system simulator, and 3 designates an external terminal unit. In the mobile phone terminal 1, the reference numeral 10 designates a microphone, 11 designates a receiver, 12 designates a microphone amplifier, 13 designates a receiver amplifier, 14 designates an A/D converter, 15 designates a D/A converter, 16 designates a speech coder/decoder, 17 designates a terminal adapter, 18 designates a data communication port, 19 designates a radio interface, 20 designates an antenna, 21 designates a transmitting side speech signal path switch, 22 designates a receiving side speech signal path switch, and 23 designates a DAI port. In the system simulator 2, the reference numeral 40 designates a DAI port, 41 designates an evaluation signal storage, 42 designates a radio interface, 43 designates an antenna, and 44 designates a control and signal evaluation section.
Next, the operation will be described.
First, operations of the individual components as shown in FIG. 10 will be described. As for the components in the mobile phone terminal 1, the microphone 10 gathers input voice, and converts it into an analog electric signal. The microphone amplifier 12 amplifies the analog electric signal. The A/D converter 14 converts the amplified analog electric signal into a 13-bit linear PCM digital speech signal at 8000 samples per second. On the other hand, the D/A converter 15 converts the 13-bit linear PCM digital speech signal at 8000 samples per second fed from the receiving side speech signal path switch 22 into an analog electric signal. The receiver amplifier 13 amplifies the analog electric signal. The receiver 11 converts the amplified analog electric signal into voice, and radiates it to external space.
The speech coder/decoder 16 codes the 13-bit linear PCM digital speech signal at 8000 samples per second fed from the transmitting side speech signal path switch 21 to a code sequence, and decodes a code sequence fed from the radio interface 19 into the 13-bit linear PCM digital speech signal at 8000 samples per second. The radio interface 19 modulates the code sequence and transmits it via the antenna 20, and demodulates the signal received by the antenna 20.
The DAI port 23 exchanges a signal with the system simulator 2 in response to the switching state of the transmitting side speech signal path switch 21 or of the receiving side speech signal path switch 22. The signal transmission rate of the DAI port 23 is 104 kbits/second in both directions. It is based on the calculation of the evaluation speech signal: 8000 (samples/second)×13 (bits)=104,000 (bits/second).
On the other hand, the terminal adapter 17 exchanges with the radio interface 19 the digital transmission and reception data transferred to and from the external terminal unit 3 via the data communication port 18. Typically, a personal computer (called PC from now on) is connected to the data communication port 18 as the external terminal unit 3 via a modem so that it can transmit or receive e-mail via a mobile telephone line, or gain access to a network. As a result, it is necessary for the data communication port 18 to transfer a signal different from the 13-bit linear PCM digital speech signal at 8000 samples per second which is exchanged via the DAI port 23. Accordingly, the data communication port 18 must be installed separately from the DAI port 23, making it impossible to use a common port for them.
As for the individual operations of the transmitting side speech signal path switch 21 and receiving side speech signal path switch 22 as the components of the mobile phone terminal 1, they will be described later along with the concrete operation of the mobile phone terminal 1 with reference to FIGS. 11-14.
The control and signal evaluation section 44 of the system simulator 2 transmits the evaluation signal or evaluation code sequence stored in the evaluation signal storage 41 to the DAI port 40 or radio interface 42, transfers the evaluation signal or evaluation code sequence supplied from the DAI port 40 or radio interface 42 to the evaluation signal storage 41, and sends to the DAI port 40 a setting control signal on the mobile phone terminal 1 side, which is necessary for each test condition. The radio interface 42 and antenna 43 establish a radio connection with the antenna 20 and radio interface 19 of the mobile phone terminal 1 to exchange the setting control signal and evaluation code sequence with the mobile phone terminal 1 side.
Next, the operation of the transmitting side speech signal path switch 21 and receiving side speech signal path switch 22 will be described. Here, the transmitting side speech signal path switch 21 is composed of two switching devices 21-1 and 21-2, and the receiving side speech signal path switch 22 is composed of two switching devices 22-1 and 22-2. As for the operation of the mobile phone terminal 1 which is connected with the system simulator 2 via the radio connection and DAI, the ETSI standards specifies four test functions: normal operation; evaluation of a speech decoder; evaluation of a speech coder; and evaluation of a microphone, receiver, A/D converter, and D/A converter. One of the four functions is set by the individual switching devices 21-1, 21-2, 22-1 and 22-2 of the transmitting side speech signal path switch 21 and receiving side speech signal path switch 22. Here, the control information required for the setting is sent from the system simulator 2 to the transmitting side speech signal path switch 21 and receiving side speech signal path switch 22 via the DAI ports 40 and 23.
In the normal operation, the switching devices 21-1, 21-2, 22-1 and 22-2 of the transmitting side speech signal path switch 21 and receiving side speech signal path switch 22 are each connected to the a-position as shown in FIG. 11. Thus, the A/D converter 14 and the D/A converter 15 are connected to the speech coder/decoder 16 so that no digital speech signal is exchanged between the mobile phone terminal 1 and the system simulator 2 via the DAI ports 23 and 40.
In the evaluation of the speech decoder, the switching device 22-1 of the receiving side speech signal path switch 22 is connected to the b-position with the remaining switching devices 21-1, 21-2 and 22-2 being connected to the a-position as shown in FIG. 12. Thus, the speech code sequence sent from the system simulator 2 to the mobile phone terminal 1 via the radio connection is decoded by the speech decoder in the speech coder/decoder 16, and is sent back to the system simulator 2 via the b-position of the switching device 22-1 of the receiving side speech signal path switch 22. The system simulator 2 compares it with a digital speech signal which is prepared in advance in the control and signal evaluation section 44. If they disagree, the system simulator 2 makes a decision that the speech coder/decoder 16 of the mobile phone terminal 1 has a problem in its decoding process.
On the other hand, in the evaluation of the speech coder, the switching device 21-1 of the transmitting side speech signal path switch 21 is connected to the b-position with the remaining switching devices 21-2, 22-1 and 22-2 being connected to the a-position as shown in FIG. 13. Thus, a signal supplied from the system simulator 2 to the mobile phone terminal 1 is sent to the speech coder/decoder 16 via the b-position of the switching device 21-1 of the transmitting side speech signal path switch 21. The signal is coded by the speech coder, and then sent back to the system simulator 2 via the radio connection. The system simulator 2 compares it with a speech encoding result which is prepared in advance in the control and signal evaluation section 44. If they disagree, it makes a decision that the speech coder/decoder 16 has a problem in its coding process.
In the evaluation of the microphone, receiver, A/D converter and D/A converter, the switching device 21-1 of the transmitting side speech signal path switch 21 is connected to the a-position, the switching device 21-2 is connected to the b-position, the switching device 22-1 of the receiving side speech signal path switch 22 is connected to the a-position and the switching device 22-2 is connected to the b-position as shown in FIG. 14. In FIG. 14, the reference numeral 50 designates an evaluation signal generator, 51 designates an artificial mouth amplifier, 52 designates an artificial mouth, 53 designates an artificial ear, 54 designates an artificial ear amplifier, and 55 designates a signal evaluation unit, which are used in the evaluation of the microphone, receiver, A/D converter and D/A converter.
First, the operation of the evaluation of the microphone 10 and A/D converter 14 will be described. The artificial mouth amplifier 51 amplifies the evaluation signal fed from the evaluation signal generator 50, and the artificial mouth 52 radiates it as evaluation speech. The evaluation speech is gathered by the microphone 10, amplified by the microphone amplifier 12, and converted into a digital speech signal by the A/D converter 14. The digital speech signal is sent to the system simulator 2 via the b-position of the switching device 21-2 of the transmitting side speech signal path switch 21, so that the control and signal evaluation section 44 evaluates the frequency characteristic of the microphone 10 and A/D converter 14.
Next, the operation of the evaluation of the receiver 11 and D/A converter 15 will be described. The 13-bit linear PCM digital speech signal at 8000 samples per second of −26 dBov, which is prepared in advance, is sent from the system simulator 2 to the mobile phone terminal 1. It passes through the b-position of the switching device 22-2 of the receiving side speech signal path switch 22, and is supplied to the D/A converter 15 that converts it into an analog electric signal. The analog electric signal is amplified by the receiver amplifier 13, and is converted into sound by the receiver 11 to be radiated to the space. The sound is gathered by the artificial ear 53, amplified by the artificial ear amplifier 54, and is subjected to the frequency characteristic analysis by the signal evaluation unit 55.
The acoustic echo evaluation of the mobile phone terminal 1 is carried out as follows. First, the system simulator 2 sends the digital speech signal in the same manner as in the evaluation of the receiver and D/A converter. The sound the receiver 11 radiates is gathered by the microphone 10, and the signal is sent back to the system simulator 2 in the same manner as in the evaluation of the microphone and A/D converter. The control and signal evaluation section 44 compares the signal level difference between the two signals, and compares it with a specified value, thereby completing the acoustic echo evaluation of the mobile phone terminal 1.
Incidentally, as for documents relevant to the conventional mobile phone terminal, there are Japanese patent application laid-open No. 2000-139032, and Japanese patent application laid-open No. 9-83632. The former discloses an apparatus of carrying out communication with an external device such as a PC via a battery charger using a USB interface mounted on the apparatus. The latter discloses a handsfree adapter using the DAI in a GSM terminal.
With the foregoing configuration, the conventional GSM mobile phone terminal carries out the acoustic evaluation tests as described above. Therefore, it must possess the physical interface (DAI port 23) specified for the DAI. Today, these mobile phone terminals often include a general purpose external connection interface (data communication port 18) that enables the data communication with a PC. However, although they include such a general purpose data communication port 18 in their body, they must also include the DAI port 23 separately for the acoustic evaluations. Thus, the conventional mobile phone terminal has a problem of reducing its size and weight.
In addition, the conventional GSM mobile phone terminal and its acoustic evaluation test have the following problems because the DAI port 23 is located between the speech coder/decoder 16 and the A/D converter 14 and D/A converter 15, because the signal exchanged between the mobile phone terminal 1 and the system simulator 2 via the DAI ports 23 and 40 is limited to the 13-bit linear PCM digital speech signal at 8000 samples per second only, and because it is essential to establish the connection with system simulator 2 via the radio connection in the test of the speech coder/decoder 16 to exchange the code sequence.    (1) Since the mobile phone terminal 1 and the system simulator 2 must comprise the radio interfaces 19 and 42 and antennas 20 and 43 for establishing the radio connection, it is unavoidable that the size of the evaluation system becomes large.    (2) When a combination with the radio interface 19 cannot be established in a special condition in the development stage of the terminal, the individual operation test of the speech coder/decoder 16, or of the A/D converter 14, D/A converter 15 and analog circuit section cannot be achieved independently.    (3) The error rate can increase depending on the operation condition of the radio connection, thereby causing instability of the operation of the evaluation system.
Likewise the conventional GSM mobile phone terminal and its acoustic evaluation test have another problem of being unable to conduct the characteristic evaluation of the radio interface alone because the DAI port 23 is located between the speech coder/decoder 16 and the A/D converter 14 and D/A converter 15, and because the signal exchanged between the mobile phone terminal 1 and the system simulator 2 via the DAI ports 23 and 40 is limited to the 13-bit linear PCM digital speech signal at 8000 samples per second only.